The invention relates to a locking device for an adjustable vehicle seat, e.g., for a vehicle seat shiftable in longitudinal direction.
In the multi-ratchet locking device previously known from European patent 408 932 locking of at least one ratchet tooth is effected at a partial area of a lateral flank of said ratchet tooth, which extends at an acute angle to the locking direction. This ratchet tooth does not completely snap in during the locking process but comes into contact at various positions along the partial area extending at an acute angle to the locking direction with the appropriate locking.
Depending on the locking condition of the multiple ratchet teeth only a few engage into the locking gaps, sometimes merely two ratchet teeth. Complete locking is achieved by two ratchet teeth. Of these two ratchet teeth one tooth effects blocking in one direction of the adjustment direction while the other tooth, with its opposed flank, effects blocking in the other direction of adjustment. The other ratchet teeth come to lie disengaged on the lockings; they are not required for this particularly adjusted locking process. However, they are necessary for locking engagement at other relative positions between snap-in bar and locking device.
The previously known locking device is particularly suitable for manually operated locking devices of adjustable vehicle seats; for example, for locking the longitudinal adjusting device of a rest joint fitting etc. When performed in practice, operating is effected with an operating device and is effected by means of a bowden rope, for example. When the operating device is drawn and stretched against the force of the springs preloading the individual ratchet teeth in locking direction, a releasing device will lift or draw the ratchet teeth into a release position, i.e., out of engagement with the lockings. The release device is designed as a drag clutch; it initially acts on at least one ratchet tooth protruding farthest in locking direction, lifts it up, subsequently lifts the other ratchet teeth protruding to a lesser extent in locking direction and eventually, takes along those ratchet teeth lying on the lockings.
In practical operation, the operator will experience a graduated operating force. Initially, when only one ratchet tooth or a few ratchet teeth are drawn, the force for release is low. However, the force will increase abruptly when the disengaged ratchet teeth lying on the lockings are likewise lifted and drawn free in the further course of the release motion. During the release motion, the operator will experience a stepwise occurring force.
In specific cases of relative positions between snap-in bar and locking unit, this graduation will be particularly significant when only two ratchet teeth are in engagement and the other ratchet teeth lie on the lockings without engagement. In this case a user, when operating the release device, might misinterpret the level of force that he feels as the disengaged ratchet teeth also come free with proceeding release motion and conclude that this already is the final stop of the release device and thus, as the end of the motion which he has to carry out for release. In this case, however, release is not yet achieved. Even if he does not make this mistake, a graduated operating force in release direction is unfamiliar and misleading for the user.
Now, this is where the invention commences. It has the objective to further advance the known locking device of the type mentioned at the beginning in such way that without changing the practically stepless locking at any relative position whatsoever, more than half of the ratchet teeth will engage in locking gaps if ever possible, so that the number of ratchet teeth lying on the lockings without engagement will be as low as possible, and a user, when operating the release device in the direction of release, will experience a level of force as low as possible when moving the non-engaged ratchet teeth as well into release position subsequently to the engaged ones.
Starting from the locking device mentioned at the beginning, the objective is attained in that for periodic measure P, there is provided a short locking gap, a first locking, a long locking gap, and a second locking corresponding in width to the first locking, with the long locking gap being at least 1.5 times as wide as the short locking gap, and with both lockings together making up for less than 40%, preferably less than 25% of the periodic measure P.
In said locking device, there are provided two different locking gaps in periodic and alternating fashion, namely, a short and a long one. In the selected description of claim 1 the periodic measure P is defined in such way that each period consists of a short and a long locking gap and of two lockings equal in width. The corresponding locking unit with n locking teeth of the same construction arranged at equal distances has an overall width corresponding to the sum of n times b plus (n-1) times z, wherein b is the width of a locking tooth and z is the distance between two locking teeth. The overall width may be smaller and, preferably, is smaller than the measure P; e.g., it is 0.8 times P.
In terms of proportion, the snap-in bar of the locking device according to the invention has more gaps than lockings; the locking gaps together make up for at least 60%, preferably at least 75% of the length of the snap-in bar while the lockings make up for only 25%, preferably 20%. In this way, the probability that one of the ratchet teeth encounters a locking is relatively low. In other words, of n ratchet teeth in the locking device according to the invention, at least 3/5, preferably at least 3/4 and, in particular, at least 4/5 do snap in more or less. In this way, the stage during dragging free of the individual ratchet teeth is determined by disengaged ratchet teeth to merely a minor extent. In particular, when dragging free, it is not the case that multiple ratchet teeth lying on the lockings will come free all of a sudden; rather, the force during dragging free is diversely graduated.
It has proven particularly advantageous to select the distance between two adjacent ratchet teeth in the region of the tooth tips greater than the width of a locking and the distance of two adjacent ratchet teeth in the region above this partial area smaller than the width of a locking. Then, lock is established in that two adjacent ratchet teeth come to lie left and right at a locking. Of these two ratchet teeth one has completely snapped in and thus makes contact above its slanted extending partial area with the locking; the other one has snapped in in such way that lock occurs at the partial area. Independent of tolerances, a precise and slack-free lock is always attained in this way. Each such lock requires only two ratchet teeth. The additional ratchet teeth are not necessary for this specific lock but effect a lock when the locking unit is shifted by a small proportion of the periodic measure with respect to the snap-in bar. In other words, the additional ratchet teeth result in locks at positions which are only slightly away from the lock positions of the ratchet teeth in question. Thus, a highly fine-stepped though not stepless lock is achieved in this way.
It has proven very advantageous to design the short locking gaps in circular shape and to devise the long locking gaps as slots limited by half circular arcs having the radii of the short locking gaps. Then, the ratchet teeth are designed in a round shape and have a radius smaller than the radius of the circular short ratchet teeth; preferably, it is smaller than 70% of this radius, in particular, even smaller than 60%. This locking device can be produced favorably. Due to the differences in diameter, defined contacts are achieved. It is possible to achieve by means of rotation that the ratchet teeth will not wear on one side.
Proven to be particularly advantageous are locking units having four ratchet teeth; here, in the normal case, three ratchet teeth are always locked into the snap-in bar, and merely one ratchet tooth lies on a locking without engagement. The constructive input with four ratchet teeth is still tolerable; however, the locking effect is qualitatively good due to the three ratchet teeth being engaged normally.
At any relative position between locking unit and snap-in bar, the locking device according to the invention will always result in engagement of at least one ratchet tooth in one of the locking gaps. Here, lock is always achieved which also withstands acceleration forces due to accidents. However, such a lock is not always free of slack. Frequently, for a slack-free lock between locking unit and snap-in bar a relative motion between these two parts is required. In case this occurs, another ratchet tooth will engage at least so far until a slack-free lock is reached. Thus, a distinction is to be made between the first step of lock wherein a sufficiently secure connection between locking unit and snap-in bar is always achieved, i.e., independent of the relative position between snap-in bar and locking unit, and a slack-free lock which cannot be achieved at any relative position but, starting from the first step of lock, is achieved with minor relative motions such as regularly occurring due to movements of the passenger or acceleration of the motor vehicle.